What is vss2svn?
This is an old answer from the old project page with some editorial changes: vss2svn is a Perl script to migrate revision history from a Microsoft Visual SourceSafe (VSS) database to the Subversion version control system. It will migrate all as much history as possible with the command-line client including revision history, including comments, author names, and optionally revision dates (migrating dates uses a not-officially-supported feature of Subversion and can only be done if you are migrating to a brand-new Subversion repository).